Re: Can I get some rules help with PARSE::RECDESCENT

I know I am missing something fundamental... I don't have any Idea where that array ref is coming from

Have you taken a look at Some Tips(from a beginner) for using Parse::RecDescent:

I suggest Dumping @item as the first line in an action and not writing any additional code in the action until you examine the output.

Eventually, your expr rule gets an @item array that looks like this:

expr rule:
$VAR1 = [
          'expr',
          'cvtype=\'problem\'',
          [
            {
              'and ' => 'problem_description match \'*\''
            }
          ]
        ];
[download]

Then you return the hash ref {$item[2], $item[1]}, where the key is $item[2], which is an array ref (it's surrounded by brackets in the Data::Dumper output). That's why you see:

$VAR1 = {
          'ARRAY(0xa102e8)' => 'cvtype=\'problem\''
        };
[download]

For instance:

my $href = {
    [1, 2, 3], "hello"
};

say Dumper($href);

--output:--
$VAR1 = {
          'ARRAY(0x7fe1bf803638)' => 'hello'
        };
[download]

Here's the proof:

use strict;
use warnings; 
use 5.020;
use autodie;
use Data::Dumper;

use Parse::RecDescent;

my $grammar =<<'END_OF_GRAMMAR';

    #Start up action(executed in parser namespace):
    { 
        use 5.012;  #enable say() 
        use Data::Dumper;
    }

    startrule: expr
              { 
                say "startrule:";
                say Dumper(\@item);
                $return = \@item;
              }


    expr: operand operation(s?)
          {   
            say "expr rule:";
            say Dumper(\@item);
            my $result = @{$item[2]} ? { $item[2], $item[1]} : $item[1
+];
            say 'Inside expr rule: $result=';
            say Dumper($result);
            $return = $result;
         }

    operation: /and | or/ operand 
               {
                say "operation rule:";
                say Dumper(\@item);
                $return = { $item[1], $item[2] };
               }

  operand: '(' expr ')'
            { 
                say "operand rule:";
                say Dumper(\@item);
                $return = $item[2];
            }

            | term {say "term rule:";say Dumper(\@item);$item[1] }

  term: /[\w\s=><\/:"'\*_]+/

END_OF_GRAMMAR

my $input = "(cvtype='problem') and (problem_description match '*')";
print "Text: $input\n";

my $parser = Parse::RecDescent->new($grammar);
my $result = $parser->startrule($input) or die "Could Not Parse!\n";

say '$result:';
print Dumper $result;

--output:--
Text: (cvtype='problem') and (problem_description match '*')
term rule:
$VAR1 = [
          'operand',
          'cvtype=\'problem\''
        ];

expr rule:
$VAR1 = [
          'expr',
          'cvtype=\'problem\'',
          []
        ];

Inside expr rule: $result=
$VAR1 = 'cvtype=\'problem\'';

operand rule:
$VAR1 = [
          'operand',
          '(',
          'cvtype=\'problem\'',
          ')'
        ];

term rule:
$VAR1 = [
          'operand',
          'problem_description match \'*\''
        ];

expr rule:
$VAR1 = [
          'expr',
          'problem_description match \'*\'',
          []
        ];

Inside expr rule: $result=
$VAR1 = 'problem_description match \'*\'';

operand rule:
$VAR1 = [
          'operand',
          '(',
          'problem_description match \'*\'',
          ')'
        ];

operation rule:
$VAR1 = [
          'operation',
          'and ',
          'problem_description match \'*\''
        ];

expr rule:
$VAR1 = [
          'expr',
          'cvtype=\'problem\'',
          [
            {
              'and ' => 'problem_description match \'*\''
            }
          ]
        ];

Inside expr rule: $result=
$VAR1 = {
          'ARRAY(0x7fb68384ac98)' => 'cvtype=\'problem\''
        };

startrule:
$VAR1 = [
          'startrule',
          {
            'ARRAY(0x7fb68384ac98)' => 'cvtype=\'problem\''
          }
        ];

$result:
$VAR1 = [
          'startrule',
          {
            'ARRAY(0x7fb68384ac98)' => 'cvtype=\'problem\''
          },
          $VAR1
        ];
[download]

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